Resistive Implant Welding of Thermoplastic Materials with Butt Joints

ABSTRACT

A method for forming butt joints between thermoplastic members by resistive implant welding. A tongue is formed on one member to be joined and a complementary groove is formed in the other member. A resistive implant is placed between the tongue and the groove which are then pressed together by an applied pressure. An electric current is run through the resistive implant to melt a portion of the thermoplastic material of both the tongue and groove, and the melted plastic intermingles through the implant. When the electric current is removed, the plastic cools, forming a weld.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a PCT International Application of U.S. PatentApplication No. 61/007,239 filed on Dec. 11, 2007. The disclosure of theabove application is incorporated herein by reference. This applicationclaims the benefit of U.S. Provisional Application No. 61/007,239, filedDec. 11, 2007.

FIELD OF THE INVENTION

The present invention relates to resistive implant welding ofthermoplastic components. More specifically, the present inventionrelates to a method and system for forming butt joints of thermoplasticcomponents using resistive implant welding.

BACKGROUND OF THE INVENTION

A need exists to join thermoplastic components, such as those formedfrom glass fiber reinforced polypropylene or the like, to other plasticcomponents formed of similar materials. To date, such joining has beenachieved via adhesives, mechanical fasteners, laser welding and/or sonicor vibration welding.

More recently, lap welds have been formed to join thermoplasticcomponents using resistive implant welding techniques. In general, thetechnology of forming lap welds with resistive implant welding isdescribed in, “Resistive Implant Welding of Glass Fiber ReinforcedPolypropylene Compounds”, by Bates, Tan, Zak and Mah, published by theSociety of Automotive Engineers, SAE Technical Papers, document number2006-01-0332 and the contents of this paper are included herein, in itsentirety, by reference.

While resistive implant welding is proving to be a promising techniquefor forming lap welds between thermoplastic materials, to date resistiveimplant welding techniques have only been able to form lap welds whichlimits the use of these techniques.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a novel method andsystem for using resistive implant welding to form butt joints ofcomponents formed of thermoplastic materials which obviates or mitigatesat least one disadvantage of the prior art.

According to a first aspect of the present invention, there is provideda method of forming a welded butt joint between first and secondthermoplastic components, the method comprising the steps of: forming atongue along an edge of a first thermoplastic component to be joined;forming a groove along an edge of a second thermoplastic component to bejoined; inserting the tongue into the groove with a resistive implantlocated therebetween; applying pressure to the first thermoplasticcomponent and the second thermoplastic component to urge the tongue intothe groove while applying an electric current to the resistive implantfor a pre-selected time to melt a portion of the thermoplastic materialof the tongue and groove; and removing the electric current and allowingthe melted thermoplastic material to resolidify while maintaining thepressure to form a welded butt joint between the first and secondthermoplastic components.

The present invention provides a method for forming butt joints betweenthermoplastic members by resistive implant welding. A tongue if formedon one member to be joined and a complementary groove is formed in theother member. A resistive implant is placed between the tongue and thegroove which are then pressed together by an applied pressure. Anelectric current is run through the resistive implant to melt a portionof the thermoplastic material of the tongue and groove and the meltedplastic intermingles, through the implant. When the electric current isremoved, the plastic cools, forming a weld.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will now be described, byway of example only, with reference to the attached Figures, wherein:

FIG. 1 shows a first exploded view of the rear sides of a pair ofthermoplastic components to be joined, according to the presentinvention;

FIG. 2 shows a second exploded view, similar to that of FIG. 1, whereina resistive implant has been positioned between a pair of thermoplasticcomponents to be joined, according to the present invention;

FIG. 3 shows a sectional side view of the components shown in FIG. 2;and

FIG. 4 shows sectional side view of the component of FIG. 2, where thepair of thermoplastic components are positioned relative to one anotherbefore the weld has been formed.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term “plastic” is intended to comprise thermoplasticmaterials in general and such thermoplastic materials can include addedmaterials, such as glass fibers, to alter their mechanical properties.While some of the following discussion makes specific reference to glassfiber reinforced polypropylene plastics, the present invention is notlimited to use with this particular reinforced thermoplastic material.

As discussed above, resistive implant welding is known. In general, thetechnology of resistive implant welding is described in, “ResistiveImplant Welding of Glass Fiber Reinforced Polypropylene Compounds”, byBates, Tan, Zak and Mah, published by the Society of AutomotiveEngineers, SAE Technical Papers, document number 2006-01-0332 and thecontents of this paper are included herein, in its entirety, byreference.

However, existing resistive implant welding is used to connect plasticcomponents via lap joints. In many circumstances, it is desired to havecomponents joined by a butt joint. In particular, as lap joints resultin joints with changing profiles, butt joints would be preferred forjoints on cosmetically significant thermoplastic components, such asexterior body panels on a vehicle.

To address this issue, the present inventors have developed structuresand methods for joining two or more panels of thermoplastic materialsvia butt joints.

Specifically, FIG. 1 shows edge portions of a first panel 20 and asecond panel 24, each of which is formed of a thermoplastic material,which are to be joined by a butt joint.

Referring to the Figures generally, the first panel 20 includes a groove28 along the rear face of the first panel 20 at the edge to be joined.The first panel 20 also includes a small notch 32 along the front faceof panel 20 adjacent the edge to be joined.

As is also shown, the second panel 24 includes a tongue 36, which iscomplementary in shape to the groove 28. The tongue 36 runs along therear face of second panel 24 at the edge to be joined. The second panelalso includes a flange 40 which is complementary in shape to the notch32, and the flange 40 extends along the edge of second panel 24.

Second panel 24 further includes a series of support members 44, whichextend at intervals along the edge of second panel 24 to be joined. Eachof the support members 44 extend perpendicularly from the rear side ofthe second panel 24, and each of the support members 44 also include aslot 48 which abuts the rear outer surface of groove 28.

Each of the first panel 20 and second panel 24 may be formed in anyappropriate manner, such as by injection molding, which can be used toform the panels 20 and 24 in the desired manner with the above-describedstructures, including groove 28, notch 32, tongue 36, flange 40 andsupport members 44.

When it is desired to join first panel 20 and second panel 24 with abutt weld, a resistive implant 60 is placed between tongue 36 and groove28, as shown in FIGS. 2 and 3. In a presently preferred embodiment ofthe invention, resistive implant 60 is a stainless steel mesh with wiresof 0.009 inches diameter woven in a plain weave of sixteen wires to theinch. However, as will be apparent to those of skill in the art, thepresent invention is not limited to this type or configuration ofresistive implant, and any suitable resistive element, as will occur tothose of skill in the art, may be employed.

When resistive element 60 is properly placed, tongue 36 of second panel24 is inserted into groove 28 of first panel 20, as shown in FIG. 4. Thedimensions of the groove 28 and tongue 36 are selected such that, whenthe resistive implant 60 is in place, a substantially tight fit isobtained between the tongue 36 and groove 28 to avoid any gaps, voids,or other empty volumes, except any such volumes resulting from thestructure of resistive implant 60, such as the gaps in the mesh if aresistive implant with a mesh structure is employed.

Pressure is then applied, as indicated by arrows 64 and 68 in FIG. 4, tothe interface between tongue 36 and groove 28. An electric current isthen passed through resistive implant 60 resulting in the heating of theinterface between the groove 28 and the tongue 36, melting thethermoplastic material. The melted thermoplastic material of the groove28 and the melted thermoplastic material of the tongue 36 interminglethrough the mesh of the resistive implant 60 because of the pressureapplied to the first panel 20 and the second panel 24.

After a pre-selected time, the electric current is removed from theresistive implant 60, the joint formed between the groove 28 and thetongue 36 is allowed to cool, and the pressure applied to first panel 20and second panel 24 is then removed. When sufficiently cooled, the jointbetween the panels 20 and 24 is complete.

Notch 32 and flange 40 serve to provide a smooth surface to the weld onthe front face of panels 20 and 24, and prevent any over-engagement ofpanels 20 and 24 during the welding operation. Further, the notch 32 andflange 40 cooperate with the support members 44 to prevent any bendingmoment about the interface between the groove 28 and the tongue 36during the welding operation.

As should be apparent to those of skill in the art, while it ispresently preferred that support members 44 be integrally formed on atleast the second panel 24, it is also contemplated that support members44 may be omitted, and support instead may be provided by a die or otherforming member which is placed adjacent the rear of the groove 28 duringthe welding operation.

The present invention provides a method for forming butt joints betweenthermoplastic members by resistive implant welding. A tongue is formedon one member to be joined and a complementary groove is formed in theother member. A resistive implant is placed between the tongue and thegroove which are then pressed together by an applied pressure. Anelectric current is run through the resistive implant to melt a portionof the thermoplastic material of the tongue and groove; the meltedplastic of the tongue and groove intermingles through the implant. Whenthe electric current is removed, the plastic cools, forming a weld.

The above-described embodiments of the invention are intended to beexamples of the present invention and alterations and modifications maybe effected thereto, by those of skill in the art, without departingfrom the scope of the invention which is defined solely by the claimsappended hereto.

1. An assembly connected together through the use of resistive implant welding, comprising: a first panel; a groove formed in a portion of said first panel; a second panel; a tongue portion formed on a portion of said first panel, said tongue portion complementary in shape in relation to said groove; and a resistive implant operable for being substantially disposed within said groove such that when said tongue portion is positioned in said groove, said resistive implant is positioned between said tongue portion and said groove, and a current is applied to said resistive implant, generating heat to join said tongue portion and said groove, thereby joining said first panel to said second panel.
 2. The assembly connected together through the use of resistive implant welding of claim 1, further comprising: a notch extending along and formed on a portion of said first panel, said notch being substantially parallel to said groove formed in a portion of said first panel; and a flange extending along said second panel, said flange being complementary in shape to said notch such that when said first panel is joined to said second panel, said flange will be engaged with said notch.
 3. The assembly connected together through the use of resistive implant welding of claim 1, further comprising: at least one support member formed on a portion of said second panel; and at least one slot formed between said at least one support member and said tongue portion, said at least one slot abutting a rear outer surface of said groove when said tongue portion is disposed in said groove.
 4. The assembly connected together through the use of resistive implant welding of claim 3, wherein said at least one support member is operable for preventing a bending moment about said groove and said tongue when said tongue is disposed in said groove.
 5. The assembly connected together through the use of resistive implant welding of claim 1, wherein pressure is applied to said first panel and said second panel as said resistive implant is heated to facilitate said first panel being joined with said second panel.
 6. The assembly connected together through the use of resistive implant welding of claim 1, said resistive implant further comprising a wire mesh.
 7. The assembly connected together through the use of resistive implant welding of claim 6, said wire mesh further comprising wires of substantially 0.009 inches in diameter.
 8. The assembly connected together through the use of resistive implant welding of claim 6, said wire mesh further comprising a plain weave of approximately sixteen wires per inch.
 9. The assembly connected together through the use of resistive implant welding of claim 1, wherein as a current is applied to said resistive implant, a portion of said groove will melt and a portion of said tongue portion will melt, and when said groove and said tongue portion are allowed to cool, said tongue portion will be joined to said groove.
 10. An assembly connected together through the use of resistive implant welding comprising: a first panel; a groove formed in a portion of said first panel; a notch formed in said first panel, said notch extending along said first panel and is substantially parallel to said groove; a second panel; a tongue portion formed in a portion of said second panel, said tongue portion complementary in shape to, and operable for being positioned in, said groove; a flange formed on said second panel and complementary in shape to said notch, said flange being operable to be engaged with said notch when said tongue portion is positioned in said groove; and a resistive implant operable for being positioned in said groove and in contact with said tongue portion when said tongue portion is positioned in said groove such that when a current is applied to said resistive implant, heat is generated, causing a portion of said tongue portion to melt, and a portion of said groove to melt, and a melted portion of said tongue portion will join a melted portion of said tongue portion after said tongue portion and said groove are allowed to cool.
 11. The assembly connected together through the use of resistive implant welding of claim 10, further comprising: at least one support member formed on a portion of and extending away from said second panel; and at least one slot formed between said at least one support member and said tongue portion, said at least one slot operable for receiving an outer surface of said groove.
 12. The assembly connected together through the use of resistive implant welding of claim 11, wherein said at least one support member is operable for preventing a bending moment about said groove and said tongue when said tongue is disposed in said groove.
 13. The assembly connected together through the use of resistive implant welding of claim 10, wherein as said current is applied to said resistive implant, a pressure is applied to said first panel and said second panel, further joining said first panel to said second panel.
 14. The assembly connected together through the use of resistive implant welding of claim 10, said resistive implant further comprising a wire mesh configured as a plain weave of approximately sixteen wires per inch.
 15. The assembly connected together through the use of resistive implant welding of claim 14 said wire mesh further comprising wires of substantially 0.009 inches in diameter.
 16. The assembly connected together through the use of resistive implant welding of claim 10, wherein as a current is applied to said resistive implant, said melted portion of said tongue portion and said melted portion of said groove will interface through said resistive implant.
 17. A method of forming a welded butt joint between first and second thermoplastic components, the method comprising the steps of: providing a first thermoplastic component; providing a second thermoplastic component to be joined with said first thermoplastic component; providing a resistive implant operable for facilitating the joining of said first thermoplastic component to said second thermoplastic component; forming a groove along an edge of said first thermoplastic component; forming a tongue along an edge of said second thermoplastic component; inserting said tongue into said groove with said resistive implant located therebetween; applying pressure to said first thermoplastic component and said second thermoplastic component to urge said tongue into said groove while applying an electric current to said resistive implant for a pre-selected time to melt a portion of said thermoplastic material of said tongue and said groove; and removing the electric current and allowing the melted thermoplastic material to resolidify while maintaining the pressure to form a welded butt joint between said first thermoplastic component and said second thermoplastic component.
 18. The method of forming a welded butt joint between first and second thermoplastic components of claim 17, further comprising the steps of: forming a notch disposed along said first thermoplastic component, such that said notch is substantially parallel to said groove formed in said first thermoplastic component; forming a flange on a portion of said second thermoplastic component; and positioning said flange adjacent to said notch when said tongue is disposed in said groove.
 19. The method of forming a welded butt joint between first and second thermoplastic components of claim 17, further comprising the steps of: forming at least one support member on said second thermoplastic component in proximity to said tongue; forming at least one slot between a portion of said at least one support member and said tongue; and abutting said at least one slot to a rear outer surface of said groove when said tongue is disposed in said groove.
 20. The method of forming a welded butt joint between first and second thermoplastic components of claim 17, further comprising the steps of said at least one support member preventing a bending moment about said groove and said tongue when said tongue is disposed in said groove.
 21. The method of forming a welded butt joint between first and second thermoplastic components of claim 17, further comprising the steps of forming said resistive implant from a wire mesh.
 22. The method of forming a welded butt joint between first and second thermoplastic components of claim 21, further comprising the steps of forming said wire mesh from wires of substantially 0.009 inches in diameter.
 23. The method of forming a welded butt joint between first and second thermoplastic components of claim 21, further comprising the steps of forming said wire mesh from a plain weave of sixteen wires per inch. 